| Summary: | 博士 === 國立臺灣大學 === 生化學研究所 === 89 === Part I
This study has demonstrated that baicalein has anti-cancer effectiveness against human hepatoma cells. The dose response of baicalein in Hep G2 and Hep J2 cells indicates that baicalein decreased viability more than 90%. In comparison, baicalein had only minimal effects on the viability of control Chang liver cells. Flow cytometric analysis showed that baicalein inhibited the cell cycle of Hep G2 cells in the S phase. In addition, baicalein treatment resulted in a decreased mitochondrial transmembrane potential and damaged the integrity of the cell membrane. The TUNEL assay results indicated that baicalein elicited a significant increase of DNA fragmentation in Hep G2 cells after incubation for 24 and 48 hours. These results indicate that baicalein is an effective anti-hepatoma agent with minimal influence on non-cancer cells. The effects of baicalein on Hep G2 cells include inhibition of the S phase of the cell cycle. Flow cytometric studies revealed that baicalein maintained the ability to increase the presence of intracellular reactive oxygen species (ROS). Intracellular glutathione (GSH) depletion, however, did not appear apparently during the periods of baicalein treatment, suggesting that intracellular ROS generation does not constitute a critical event in baicalein-induced apoptosis. In this paper, we reveal that the mitochondrial transmembrane potential (m) decreased dramatically subsequent to baicalein treatment. On the other hand, the level of Bcl-2 decreased after 24 hours incubation of Hep G2 cells in the presence of baicalein, suggesting that the decrease of Bcl-2 may be an important element in apoptosis induced by baicalein. In addition, results indicate that cytochrome c, released from mitochondria into the cytosol. Our data are consistent with the hypothesis that baicalein could contribute to Hep G2 cell apoptosis through mitochondrial dysfunction, cytochrome c release and the initiation of apoptosis.
Part II
Shikonin has been demonstrated to exhibit anti-cancer activity, but the mechanisms are poorly understood. In this paper, we reveal that the administration of shikonin induced the cytotoxicity of the human hepatofibroblastoma G2 (Hep G2) cell line, and stimulated necrotic and apoptotic cell death. Flow cytometric studies indicated that shikonin maintained the ability of the cells to increase the presence of intracellular reactive oxygen species (ROS). In this study, we reveal that the mitochondrial transmembrane potential (m) decreased dramatically following shikonin treatment. In addition, results indicated that cytochrome c, released from mitochondria into the cytosol, and caspase-2, -3, -8, and -9, were activated during shikonin-induced apoptosis. This paper also demonstrated that shikonin induced the increasing of p53 and bax proteins expression, decreasing of Bcl-2 protein expression on Hep G2. The p53 may play an critical role in the apoptosis signiling pathway in shikonin-induced Hep G2 apoptosis.
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